Variations in the Activity of Dry-Powder Water-Repellent Mortar Admixtures with Different Mortar Formulae

A number of water repellents are added to masonry mixes and masonry units. To be classified as a water-repellent mortar admixture, ASTM C 1384 Specification for Admixtures for Masonry Mortars, requires that the 24-h rate of water absorption needs to be reduced by at least 50 % when compared to a control mortar without the admixture. While testing two well-known water-repellent admixtures, a substantial difference in activity was noted with the mortar that was being tested. Testing was expanded to include other water-repellent admixtures and several additional mortar formulae. This paper discusses the findings of that study.